Visual inspection is a common technique for analyzing equipment and systems for both maintenance and troubleshooting. Often times, the components to be inspected are housed within an enclosure for safety, operability, or other reasons. In such an instance, it may be preferable to enable visual inspection of such components while the enclosure is closed. In many cases, visual inspection cannot be performed through a solid enclosure, so in order to perform the inspection, a viewing window assembly may be installed into the enclosure. One illustrative example is infrared imaging of high voltage electrical equipment within an electrical cabinet. Although, imaging of high voltage electrical equipment within an electrical cabinet may be in many different wavelengths, including visible light wavelengths.
Infrared (IR) imaging has increasingly been used in the preventative maintenance of high voltage electrical circuits and components. An IR image of the components can often reveal hot spots which may indicate malfunctioning, improperly connected, or overloaded components. Timely identification of problem components can save on system downtime and expenses associated with replacing blown or destroyed components.
To effectively inspect electrical components, a thermographer should view the components with an IR camera while the components are operating or energized. However, this can be difficult because electrical components are often kept in high voltage electrical cabinets. Because an IR camera requires a line of sight to deliver a suitably accurate thermal image, components within a cabinet cannot be imaged adequately without either opening the cabinet or providing some other view into the cabinet.
Opening a high voltage electrical cabinet while the components within are energized poses a risk of arc flashing. To avoid this risk, most cabinets include door interlocks which require that the components within be powered off before the cabinet can be opened. But when the power is turned off the components within the cabinet begin to cool and heat within the cabinet is rapidly dissipated or redistributed. This rapid heat dissipation precludes adequate identification of hot spots in a particular thermal image.
As an alternative to imaging cool components by opening the cabinet door, the thermography industry has placed fixed IR transmitting windows in a panel or door of high voltage electrical cabinets. These windows can provide a line of sight within the cabinet so that it may be inspected without being opened while the components within are energized.
However, these windows may be difficult and/or time intensive to install into a cabinet that does not have one built into it, as they often require shutting down, opening, and/or disassembling the cabinet.
Previous IR windows aimed toward this purpose have required access to both sides of a panel that makes up a portion of the cabinet for installation. As such, the cabinet must at least be opened, if not disassembled, to permit such two-sided access to the desired panel in a way that permits the requisite amount of maneuverability for installation. Additionally, repair or replacement of such a window may require further opening and/or disassembly of the cabinet to allow the appropriate access. Furthermore, many previous windows have required multiple holes in the panel of the cabinet for installation—a first hole for holding the main, viewing portion of the window, and auxiliary holes for securing the window or window assembly to the cabinet.
Similar situations may apply to other types of inspection aside from thermal imaging as well, additionally or alternatively requiring visual inspection of equipment in the visible and/or ultraviolet wavelength regions.